One of the most universally used medical diagnostic lab procedures is the analysis of blood or a patient and identifying the red blood cell count and the white blood cell count in order to determine certain characteristics of such blood. This in turn enables medical practitioners to gain an insight into the patient's health in general and to potentially determine any unwanted intrusions into the patient's body, which could allow for diagnosing the patient.
In recent years, several sensing modalities for detecting and quantifying of biological and chemical analytes in general have been proposed. One of the conventional techniques used for detecting biological analytes in general and blood cells specifically is based on fluorescence exhibited by many analytes of interest generally and blood cells specifically. According to this technique, visible or detectable markers are attached to the blood cells in a blood sample. This method is known as staining. The markers are chosen based on their properties to attach to certain types of biological analytes in the cell but not others. This process is passive and does not change the properties of the analyte of interest but rather change the way it is detected. A complex optical assembly including high intensity optical sources, optical filters and lenses, is then used to detect frequency range of emission, which serve to characterize the analyte of interest.
In cases where the analyte is blood, once the blood sample is stained, manual detection is usually done under a microscope where stained blood cells of interest are counted. The blood count then allows the practitioner to make his or her diagnosis based on the results obtained.
Although such techniques provide good selectivity and sensitivity, the fluorescence-based sensing devices are inherently cumbersome, time consuming, expensive and accordingly, not suitable for many applications such as point-of-care diagnostics.
There is a desire in the field to achieve reliable, time efficient, and cost-effective techniques for identification and quantification of biological and chemical analytes.